Generic KY-039 Finger Heartbeat Detection Sensor Module

The KY-039 module is typically operated at 5V DC. Connect VCC to 5V and GND to ground on your Arduino or other microcontroller board. The analog signal pin can be connected directly to an analog input pin (e.g., A0).

Stable readings require minimizing ambient light interference. Place the fingertip firmly over the IR LED and phototransistor, and use a dark enclosure or finger cuff to block stray light. Implement software filtering (e.g., a low-pass filter or moving average in your code) to reduce noise from AC mains lighting and motion artifacts.

While the IR LED may illuminate at 3.3V, the output signal range will be reduced. For reliable operation with 3.3V logic boards, it is recommended to power the module's VCC pin from a 5V source (if available) and use a voltage divider or level shifter on the analog output signal to safely interface with the 3.3V analog input of the microcontroller.

The analog output provides a voltage that varies with the amount of infrared light reflected back to the phototransistor. As blood pulses through the fingertip, light absorption changes, causing a small, periodic variation in this voltage. This waveform corresponds to the heart rate and must be processed algorithmically to extract beats-per-minute (BPM).